Credit card expired. Unable to update since Nov 2018

Can anyone help. I use a credit card for my monthly payments. It has expired. When I try to update my ‘Payment details’ info it takes me to a page with the following message:
500 error, an internal server error occured. We know, we know, something went wrong. We've been notified about it and we will look into it.

Please note I have had this problem since end of Nov 2018 and have sent the message below to [email blocked] a few times (at least 6) with no response received to date. It does not even appear as if my mails are being read (used Read Receipt).